Automated analysis instruments, as are currently used routinely in microbiology, analysis, forensics and clinical diagnostics, generally carry out a sequence of continuously repeating work steps. In many of these work steps, different materials have to be mixed together as homogeneously as possible in order to supply precise examination results. The necessity for uniform mixing particularly relates to liquid samples, such as blood, serum or plasma samples. By way of example, these have to be mixed homogeneously with analysis reagents before they are supplied to an analysis unit.
By way of example, for this purpose, there are devices in the prior art that use a magnetic stirrer for mixing. However, these devices harbor the risk of contaminating the container contents by particles that can adhere to the magnetic stirrer and reach the sample with the latter.
A further known approach is offered by the cuvette rotors of the coagulation analyzers BCS® and BCS® XP from Siemens Healthcare Diagnostics. In these instruments, liquids are pipetted into different, mutually separate chambers in a cuvette rotor. Fast rotation of the rotor and the centrifugal forces occurring thereby hurl the liquids into an outer chamber, where they mix. However, this arrangement requires a plurality of chambers and a relatively complex design. By way of example, such cuvette rotors are described in EP 1008844 A1.
Additionally, EP 742435 A1 has disclosed a gripper consisting of two gripper arms that are pulled together by a spring. This gripper is attached to a holding element coupled to a transfer arm. The combination of transfer arm and holding element can be e.g. part of a robotic station for treating, manipulating and analyzing chemical, clinical and/or biological samples. Here, a connection element is used to connect the holding element to a motor, which acts as a shaking apparatus by means of an eccentric. When this motor rotates, the gripper is made to oscillate. If the gripper has gripped a sample vessel with liquid contents, there is mixing of the liquid in the sample container as a result of the transmission of the oscillation from the motor to the gripper.
However, this device does not ensure that the oscillation caused by the motor also arrives at the cuvette in all cases. The inventors have observed that in certain cases the oscillations are at least partly transmitted to the transfer arm and thus oscillate e.g. the robotic station, which impairs the mixing result and can possibly even put the robotic station at risk.
Additionally, the transmission of the oscillation onto the cuvette can be impaired as soon as parts of the device get caught or jammed. Furthermore, the developing oscillation of the cuvette can have varying effects as a result of variations in or faults of involved components. This is undesirable since all cuvettes should mix as identically as possible, even over different instruments.
Additionally, the motor is also moved every time the transfer arm is moved, which can impair the functionality of the device.